1. Field of the Invention
The present invention relates to a technology of supporting the access by users to necessary information by properly arranging a group of cross-referenced documents and displaying the group of documents from various points of views.
2. Description of the Related Art
In electronic conferences, electronic news, etc. established through personal computer communications or computer networks, there has been a request to easily and quickly locate a necessary document in a set of sequentially accumulated documents.
In response to the request, a conventional technology has been developed to present the users with a list of titles obtained by rearranging the titles of documents in a set of documents in the order of document generation date.
Another conventional technology displays cross-references of documents by classifying a set of documents into groups of cross-referenced documents and displaying an indented title of each document in a group of cross-referenced documents. A further conventional technology displays cross-references of documents by displaying the numbers of the documents in a set of documents in a tree format.
A further conventional technology searches entire documents in a set of documents for a specific key word, and lists search results.
However, since the information displayed by the above described conventional technologies is limited, the following problems cannot be solved by the above described conventional technologies.    1. To retrieve a required document or a group of documents probably containing a required document from a set of various documents, the only information to be referred to is a list of titles of documents. Since all titles do not correctly describe the contents of the documents, it is hard to obtain a desired retrieval result.    2. Indented titles and document numbers in a tree structure are not enough to correctly inform a user of the entire structure of a group of documents and of the transition of the subjects in the group of documents.    3. Necessary documents cannot be accessed from various points of view.    4. When there are a number of retrieval results, required documents cannot be accessed unless limited retrieval is performed or each of the retrieval result lists is checked.
On the other hand, a technology of extracting a keyword from a plurality of specific documents and automatically setting a link from each document containing a common keyword to another document is well-known. This conventional technology enables a plurality of relevant documents to be efficiently read by setting the documents as cross-referenced in specific documents such as published patents, technological theses, etc.
However, the above described conventional technology aims at easily referencing relevant documents, and cannot be used to support the retrieval of a necessary document or a group of documents which probably contains a necessary document.